Drill



R. w. ANDREASSON 2,903,921

DRILL Filed. Oct. 9, 1957 Sept. 15, 1959 INVENTOR.

RQDOIF M ANOR'fiSSO/V A TTORA/f Y3 DRILL Rudolf .w. Andreasson,Birmingham, Mich.

Application October 9, 1957, Serial No. 689,128 11 Claims. (Cl. 77-68)This invention relates to a drill.

It is an object of the invention to provide a tube-formed drill of thetype in which a tube is straight-fluted and twisted to give the properhelical formation; reference is made to my application, Serial No.668,960 on an Oil Tube Drill, filed July 1, 1957 in which the method .offorming this type of drill shank is explained in detail.

It is an object of the present invention to improve on the previouslydisclosed drill in the formation of a tip for such drill.

As has been known, a twisted drill of this type can only be used on softmaterials unless a hard tip of some kind is fastened to the drillingend. In the absence of such a tip, a tube-formed drill has a tendency toopen up at the center due to the wedging action 10f chips'and the torqueforces on the drill. It has been customary to braze on a solid tip drilland in some way to connect up the flutes of the tip with the flutes ofthe drill. The interior passages for coolant are also either opened tothe outside of the tip or the tip is drilled to register with thesepassages. I

I have discovered that this type of oil tube drill can very easily beprovided with a suitable drill tip by slotting the formed shank in aparticular way and inserting in said slot a specially shaped pellet ofhard material such as high speed steel or carbide. 1

Other objects and features of the invention relating to details ofconstruction and operation will be apparent in the following descriptionand claims.

Drawings accompany the disclosure and the various views thereof may bebriefly described as:

Figure l, a side elevation of a completed drill.

Figure 2, a view of the tube from which the drill is formed.

Figure 3, a view of the straight-fluted tube.

Figure 4, a view of the twisted tube.

Figure 5, a sectional view of the drill.

Figure 6, a perspective view of the tip.

Figure 7, an illustration of the end of the tube prior to assembly ofthe tip.

Figure 8, a side view of the completed drill showing the side edge ofthe tip in elevation.

Figure 9, an end view of the completed drill.

Referring to the drawings:

The drill is formed from a tube 30 of carbon or chrome steel such as a41-30 steel, which has proved quite satisfactory. The tube is shaped andfluted to provide straight flutes 32 and side lands 34 and also coolantopenings 36 and 38. The tube is then twisted as shown in Figure 4. It isdesirable then to coat the tube with a hard material such as chromium asshown in Figure 5 Where the coating 40 is shown to have substantialthickness relative to the wall of the tube.

These tubes vary in wall thickness, depending on the diameter of thetube utilized. The following table shows the relationship of thediameter to the wall thickness of the tube.

nited States Patent 0 ICC . 2 Diameter of tube (inches) Wall thicknessin inches 1;, I .035 5, I p .035 l .049 K 0 I I .049 A .058 be .065 /8.072

In order to strengthen the tube against bending and torsionaldistortion, it has been discovered, as described in my previouslyidentified application, that it is possible to coat the tube with arelatively thick coating of hard material such as that described in theUnited States patent to Cole 2,694,647, issued November 16, 1944, or byanother coating which is known to the 'trade as Colmonoy coating.

Also a chromium coating will accomplish this purpose, not of the thinvariety such asis used for wear purposes or for an attractive finish,but a chromium coating of substantial thickness ranging about 20 to 30percent of the wall thickness. For example, a quarter inch tube having awall thickness of .035 inch would have a coating of about .009 inchchromium plate. A inch tube, vhaving a wall thickness of .072, wouldhave a pref erably plate coating of about .018 inch. I

This coating has been found to provide a surprisin resistance to bendingand torsional unwrapping of the drill and also has other advantages inthat the molecular adhesionbetweenthe coating and the surface of thedrill provides a useful sheath which stabilizes the entire drill,

' With a solid heat'treated drill if there is a breakage,-

there is a tendency for the parts to fragmentize fly 'through' the airand thus create a hazard to an operator.

The drill formed from tubestock will not fracture in this way. Itisunnecessary to heattreatthe drill and of course the chromium plating,in addition to strengthening the device to make it practical as a drill,also provides wear surface. I 1 I When the drill is formed, the diameteris squeezed down below the fini'sh'diameter; for example, .018 inch fora quarter inch drill and then thisdimensionis Inade np by the platecoating. i'

The tip construction of the present invention is illustrated in Figures1, 6, 8 and 9.

In the present simplified construction, I have found that I can providea slot 46 in the end of avtwisted tube diametrically between the flutesleaving a portion of the openings 36 and 38 on each side of the slot 46.Each swirl or land then projects upwardly in spaced relation with thecoolant opening being laid bare axially of the drill. The base of theslot 46 is preferably angled as shown at 48 to avoid a sharp corner andto leave more metal for the strengthening of the projecting portions ofthe drill. The slot 46 is provided to receive a small pellet 50 of toolsteel or preferably tungsten carbide, this pellet having a crownedportion 52 to complement the surfaces 48 of the slot 46. The sides 54and 56 of the pellet 50 are flat surfaces to engage and close in theopenings 36 and 38. The sides 58 and 60 of the pellet 40 are flared toprovide a proper cutting angle, and the end of the pellet is angled at62 to provide the necessary point.

The angled base of the slot is provided not only to avoid sharp cornerswhich might cause fracturing, but also to strengthen the bifurcate landsof the drill. These angled surfaces also increase the braze area andcause the drill load axially to resist the shearing force on the angledbraze area.

The pellet is preferably brazed into the slot 46 to provide cuttingedges 64 and 66 suitably spaced from the periphery of the drill. It willbe seen that the coolant 3 passages 36 and 38 are slightly ensmalled bythe cutting of the slot 46 and the insertion of the pellet 50.Nevertheless, each terminates on an opposite side of the cutting insertin close proximity to the cutting edges ,and coolant may flow throughthese passages with no further machining required.

The construction of thedrill is well suited to drills of originalmanufacture but also is readily used for re sharpening these drills. Theends may be cut off and slotted'forthe application of new tips.

' i What is claimed is as follows:

1. A 'drill'formed of a fluted and twisted tube, having coolant--.passages in spiral lands separated from each othenbyeach flute of thetool, the end of said fluted and twisted tube being opened at saidpassages on opposite sides of the center of said tool, .a slot formeddiametrically ofsaid tube removing a'central portion thereof and openingsaid passages axially of the tube at the walls of said -slot,-and aninsert of cutting material in said slot extending beyond said tubewherein said passages open onrtozathe outer :walls of said insert, andcutting edges provided on .the end of said insertprojecting from saidslot.

. ,2. .A device as defined in claim 1 in which the base of the :slot isformed of walls converging from the side walls of the slot, and the baseof the insert is shaped to compl ment thebase of said slot.

3. A drill formed of a fluted and twisted tube having interior coolantpassages in spiral lands spaced on each side of the center, :the ends ofthe formed tube being hifurcate to leave the. lands projecting axiallyand lying on pppositesides .ofspaced, parallel planes, the ends of saidcoolant-passages opening at-the inside of said spaced lands and :at the.,end of the lands, and a drill tip insert fastened insaidatubebetweensaid bifurcate ends to fill the space .therebetween andprojecting beyond said tube axially and radially, the opposite sides ofthe tip being open tos id passages at the ends of the lands.

,4. A drill as defined in claim 3 in which the inner walls of thebifurcate lands are spaced apart, each wall being interrupted axially bythe open coolant grooves which terminate at the end of the lands, saidinsert also having surfaces to block the axial extent of the coolantgroove openings.

5. 'Adrill as defined in claim '3 in which the tube is 4 formed ofrelatively tough metal and a coating of hard material molecularly bondedto said drill to create resistance to bending and torsional distortion.

6. A drill as defined in claim 5 in which the coating has a thickness ofabout 20 to 30% of the wall thickness of the tube.

7. A drill as defined in claim 6 in which the coating consists of aplating of hard metal.

8. A fluid cooled drill comprising a fluted shank including intertwinedhollow spiral flutes having coolant passages, the flutes being connectedby a solid web, one end of said shank constituting a working end, andthe opposite end constituting a holding-end, the working-end terminatingin a plane transverse to the axis, the hollow flutes being spaced atsaid working-end, to provide diametrically spaced openings, a crosspassage in said working-end extending axially into said shankeliminating the connecting web and an inside portion of each flute tointersect the coolant passages axially along said passages, and acutting element aflixed in said cross-passage having opposite facesclosing axially said flute passages in the respective flutes-anddimensioned to project beyond said flutes of said working-end to providecutting edges for I said drill.

9. A drill .as defined in claim 8 in which the opposed faces of saidcutting element in contact with a flute liein parallel planes, theremaining faces of the opposed sides flaring outwardly to cutting edges.

10. A drill as defined in claim 8 in which the base surfaces of thecross-passage and of the cutting element are formed by axially andradially inwardly converging surfaces.

11. A drill as defined in claim 8 in which the drill shank is formed ofa tube of relatively tough metal and said shank is coated with a hardmaterial molecularly bonded to the outer walls thereof in substantialthickness to create resistance to bending and torsional distortion.

References Cited in the file of this patent UNITED STATES PATENTS Re.19,182 Emmlons May 29, 1934 2,405,298 Fleischer Aug. 6, 1946 2,698,810Staulfer June 4, .1955 2,817,983 Mossberg Dec. 31, 1957

